What is Chronic Fatigue Syndrome?

Chronic fatigue syndrome (
CFS) is the common name
[1] for a group of significantly debilitating medical conditions characterized by persistent fatigue and other specific symptoms that lasts for a minimum of six months in adults (and 3 months in children or adolescents).
[2] The fatigue is not due to exertion, not significantly relieved by rest, and is not caused by other medical conditions.
[3][4] CFS may also be referred to as
myalgic encephalomyelitis (
ME),
post-viral fatigue syndrome (PVFS),
chronic fatigue immune dysfunction syndrome (
CFIDS), or by
several other terms. Biological, genetic, infectious and psychological mechanisms have been proposed, but the
etiology of CFS is not understood and it may have multiple causes.
[5][6]

Symptoms of CFS include malaise after exertion; unrefreshing sleep, widespread
muscle and
joint pain, sore throat,
headaches of a type not previously experienced,
cognitive difficulties, chronic and severe mental and physical
exhaustion, and other characteristic symptoms in a previously healthy and active person. Additional symptoms may be reported, including
muscle weakness, increased sensitivity to light, sounds and smells,
orthostatic intolerance, digestive disturbances,
depression, painful and often slightly swollen lymph nodes,
cardiac and
respiratory problems.
[7] It is unclear if these symptoms represent
co-morbid conditions or if they are produced by an underlying etiology of CFS.
[5] CFS symptoms vary in number, type, and severity from person to person.
[8] Quality of life of persons with CFS can be extremely compromised.
[9] Although
fatigue is a common symptom in many illnesses, CFS is comparatively rare.
[10] Estimates of prevalence vary from 7 to 3,000 cases of CFS for every 100,000 adults;
[5][10] national health organizations have estimated more than one million Americans and approximately a quarter of a million people in the UK have CFS.
[11][12] CFS occurs more often in women than men,
[13][14] and is less prevalent among children and adolescents.
[11] Although there is agreement that CFS poses genuine threats to health, happiness and productivity, various physicians' groups, researchers and patient advocates promote differing nomenclatures, diagnostic criteria, etiologic hypotheses and treatments, resulting in
controversy about many aspects of the disorder. The name "chronic fatigue syndrome" is controversial; many patients and advocacy groups, as well as some experts, believe the name trivializes the medical condition and they promote a name change.
[15]

The Oxford criteria (1991)[18]—includes CFS of unknown etiology and a subtype called post-infectious fatigue syndrome (PIFS). Important differences are that the presence of mental fatigue is necessary to fulfill the criteria and symptoms are accepted that may suggest a psychiatric disorder.[7]

The 2003 Canadian Clinical working definition[19]—states: "A patient with ME/CFS will meet the criteria for fatigue, post-exertional malaise and/or fatigue, sleep dysfunction, and pain; have two or more neurological/cognitive manifestations and one or more symptoms from two of the categories of autonomic, neuroendocrine, and immune manifestations; and [the illness will persist for at least 6 months]".

Naming

Chronic fatigue syndrome is the most commonly used designation,
[1] but widespread approval of a name is lacking.
[25] Different authorities on the illness view CFS as a central nervous system, metabolic, infectious or post-infectious, cardiovascular, immune system or psychiatric disorder, and different symptom profiles may be caused by various disorders.
[21] Over time and in different countries many names have been associated with the condition(s). Aside from CFS, some other names used include Akureyri disease, benign myalgic encephalomyelitis, chronic fatigue immune dysfunction syndrome, chronic infectious mononucleosis, epidemic myalgic encephalomyelitis, epidemic neuromyasthenia, Iceland disease, myalgic encephalomyelitis, myalgic encephalitis, myalgic encephalopathy,
post-viral fatigue syndrome, raphe nucleus encephalopathy,
Royal Free disease,
Tapanui flu, and yuppie flu (the last considered pejorative).
[26][27] Many patients would prefer a different name such as "myalgic encephalomyelitis", believing the name "chronic fatigue syndrome" trivializes the condition, prevents it from being seen as a serious health problem, and discourages research.
[15][28][29]

A 2001 review referenced myalgic encephalomyelitis symptoms in a 1959 article by
Acheson, stating ME could be a distinct syndrome from CFS, but in literature the two terms are generally seen as synonymous.
[30] A 1999 review explained the Royal Colleges of Physicians, Psychiatrists, and General Practitioners in 1996 advocated the use of chronic fatigue syndrome instead of myalgic encephalomyelitis or ME which was in wide use in the United Kingdom, "because there is, so far, no recognized pathology in muscles and in the central nervous system as is implied by the term ME."
[1][31] An editorial noted that the 1996 report received some acceptance, but also criticism from those advocating the use of different naming conventions, suggesting the report was biased, dominated by psychiatrists, and that dissenting voices were excluded.
[32] In 2002, a
Lancet commentary noted the recent report by the "Working Group on CFS/ME"
[33] used the compromise name CFS/ME stating, "The fact that both names for the illness were used symbolises respect for different viewpoints whilst acknowledging the continuing lack of consensus on a universally acceptable name."
[25]